Phospholipids have excellent amphiphilic and biocompatibility properties, and are used for a wide variety of purposes ranging from functional foods to medicinal products. Representative phospholipids include phosphatidyl choline (PC), phosphatidyl ethanolamine (PE), phosphatidyl inositol (PI), and phosphatidyl serine (PS). The phospholipid is used in a food additive as a lecithin-like emulsifier, and in a medicinal product as a liposome.
In recent years, awareness of omega 3 fatty acids (EPA, DHA, α-linolenic acid) has incrementally increased in Japan. α-linolenic acid is an omega 3 fatty acid which is a precursor of EPA and DHA, and has been reported (Non-Patent Literature 1, Non-Patent Literature 2) to have bioactive properties such as anti-inflammatory effects and improving cardiovascular diseases (lowering blood lipid). Cardiovascular diseases, in particular, comprise one of the three major diseases in Japan, Europe, and America, and improvement of these disorders is critical.
Exemplary sources of omega 3 fatty acids include fish, algae, linseed, and the like. In fish and algae, EPA and DHA are the primary fatty acids, whereas in linseed, α-linolenic acid is the primary fatty acid.
In particular, phospholipid-type omega 3 fatty acids are reported to have a greater effect of improving liver function, reproductive function, and brain function than ordinary triglyceride-types, and have therefore attracted attention. Exemplary sources of phospholipid-type omega 3 include krill oil, fish eggs (such as salmon), and fishery waste products. In particular, krill oil sourced from Antarctic krill is available for sale. A phospholipid omega 3 fatty acid composition derived from Antarctic krill (hill oil) has a phospholipid concentration of approximately 40% (W/W composition), and includes high-concentration triglycerides (approximately 45%) and free fatty acids (approximately 15%) (Patent Literature 1). In addition, a method has been reported of manufacturing a useful phospholipid derived from seafood, and in particular from waste products created in processing seafood (Patent Literature 2). However, when using marine products as a source, there is anxiety about heavy metals, arsenic, and the like due to oceanic pollution. Moreover, there is caution due to an instability in catch and phospholipid content due to seasonal changes. Therefore, an alternative source is sought which is unlikely to be subject to seasonal changes and which is capable of high quality, stable production. Furthermore, because lipids derived from krill oil, seafood, and the waste products thereof have phospholipid EPA and DHA as primary components, sources having phospholipid α-linolenic acid as a primary component are more preferred.
As noted above, linseed oil contains α-linolenic acid, but it is of a triglyceride type rather than a phospholipid-bound type. There are examples of attempting to prepare phospholipid α-linolenic acid from linseed oil rich in triglyceride α-linolenic acid by transesterification with an enzyme (Non-Patent Literature 3). However, because this method uses an enzyme or the like, the method requires complex operations and can potentially increase costs. Lecithin sourced from soybeans or egg yolk is common, but linoleic acid is the primary fatty acid and there is at most 10% α-linolenic acid, which is insufficient. As a dairy source, a method is given to increase phospholipid content from milk using a microfilter membrane (Patent Literature 3). However, this does not focus on increasing the content of phospholipid α-linolenic acid. In addition, using yeast as a source, a method is known of extracting fats such as linoleic acid from prototypical baker's yeast or brewer's yeast using hexane (Patent Literature 4). However, baker's yeast is known to be incapable of accumulating α-linolenic acid (Non-Patent Literature 4), and extracting phospholipids with hexane is difficult. Accordingly, there is no composition known to date which is capable of containing a large amount of phospholipid α-linolenic acid.